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Abstract

The application of large area OLEDs for lighting and signage purposes potentially requires essential changes of the common Lambert-like emission pattern. We demonstrate an array based micro optical approach for pattern shaping of area light sources based on distorted Fourier imaging of an aperture array with a micro lens array. Narrow angular emission patterns of ± 35° and ± 18° FWHM obtained experimentally demonstrate the pattern shaping with low stray light levels. The internal recycling of initially rejected photons yields intensity enhancements exceeding a factor two in forward direction that is still well below the theoretical limits due to limited reflectivity.

Figures (6)

Sketch of the system under study, comprising an OLED equipped with substrate outcoupling components and a separate pattern shaping element. All optical materials are considered to exhibit refractive index n. The shaper aperture size with respect to unit cell is α.

(a) Relative emitted power Pff/(POLED Ts) and (b) recycling enhancement Pff/(POLED α Ts) are calculated according to Eq. (4) with p = 1 for different values of the reflectivity product RSROLED and the far field NA, which is related to the aperture ration by α = NA2 in Eq. (3).